This invention is directed to a method for obtaining a tight, secure connection between two relatively non-deformable members and the connection obtained by the method. Presently, secure connections between relatively non-deformable members, such as injection molded thermoplastic parts, require the use of adhesives, mechanical fasteners, fusing, forced interference engagement or the provision of resilient webs or fingers in at least one of the parts. Each of these fastening methods adds expense to the manufacture of the products formed by the members and each method has inherent disadvantages. The inherent disadvantages of the aforesaid methods become more pronounced when the members that are to be joined must be removable and reinstallable relative to one another.
This invention overcomes the aforesaid difficulties by providing a deformable but essentially non-compressible liner between the non-deformed members which are to be attached. The tight, secure connection between the members is obtained by displacing the liner into one or more void spaces located in at least one of the members when the members are brought together to be connected.
The invention utilizes a soft moldable thermoplastic material which is displaceable and essentially non-deformable to create the interference fit between the generally non-deformable members to be connected.
This invention is particularly well suited to the molding of plastic knobs of the type which are designed to fit over a shaft formed of a hollow metal tubing such as aluminum and which are intended to be placed on and removed from a shaft.
Another object of this invention is to increase the holding capacity of a thermoplastic knob to a non-deformable shaft by providing a displaceable cushion to resist movement of the shaft engaging webs or fingers of the knob.
Yet another object of this invention is to increase the holding capacity of a thermoplastic knob to a non-deformable shaft by providing a deformable yet generally not compressible cushion between the non-deformable shaft engaging members which cushion includes a self-contained void space.
Still another object of this invention is to increase the holding capacity of a thermoplastic knob to a non-deformable shaft by providing a displaceable cushion for the shaft engaging webs or fingers of the knob and providing a constraining wall in the hub of the knob for receiving the cushion which constraining wall moves to accommodate displacement of the cushion.
Other objects of the invention will be found in the following specification, claims and drawings.